I would only if they ask me, or if I see a clear and worrying behavioral problem. Children should do as teachers say, within reason- if the teacher is abusing their position in any way, I don’t see how knowing social status helps a child. It’s more important they know their rights.
To answer the age part of your question at least, if the child understands what kings and princesses are about (very popular in children’s stories and play pretends, I’m not a royalist) then they are old enough to understand what social status is imo.